Multilayer photographic film having improved resolving power



1954 G. c. HIGGINS EIAL 2,697,036-

MULTILAYER PHOTOGRAPHIC FILM HAVING IMPROVED RESOLVING POWER Filed Nov. 23, 1949 BLUE JENS/T/VE EMULSION WITH MAGENZ I DYE I4 73 YELLOW F/LTER l2 GREEN SENSITIVE EMULSION RED SENSITIVE EMULSION SUPPORT x M BLUE JENSIT/VE :Muu/a/v mm CYAN or: 13 YELLOW mm? 15 n GREEN smsmv: EMULSION W/TH mm or: II

RED JENS/77VE EMULS/ON SUPPORT {7 w GREEN SEIVJIWVE EMULSION WITH C MN DYE RED SENSITIVE EMULSION "BLUE SENSITIVE EMULSION -5UPPORT RED .SENSlT/VE EMULSION WITH mam/m pr: GREEN SENSITIVE EMULSION BLUE .sawsrr/vs EMULSION JUPPDRT GEORGE C. HIGGHVS NICHOLAS H. GROET IN VEN TORS QM/M ATTORNEYS United States PatentfO MULTILAYER PHOTOGRAPHIC FILM HAVING IMPROVED RESOLVING POWER George C. Higgins and Nicholas H. Groet, Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey resolving power.

In the usual sensitivity arrangement of three-layer photographic film, the red-sensitive emulsion layer is.

coated adjacent the support and this is followed in order by the green-sensitive emulsion layer and the bluesensitive emulsion layer. It is customary to form a cyan dye image in the red-sensitive layer, a magenta dye image in the green-sensitive layer and a yellow dyeimage in the blue-sensitive layer. It is also known that a different sensitivity arrangement may be used in which either the red sensitive layer or the green-sensitive layer is coated outermost for the purpose of improving definition.

In any of these types of the multi-layer film, the light forming the image in the lower layers must first pass through an upper layer or layers. For example, in film having the usual sensitivity arrangement, red, green, blue from the support outward, the light forming the image in the red-sensitive layer must first pass through the bluesensitive top layer, the green-sensitive middle layer and any other layers which intervene. Since these top layers are optically turbid, they tend to impair the definition and therefore the quality of the image formed in the lower layer or layers. This is due to the light-scattering effect of the turbid upper layers and this, in turn, reduces the quality of the entire picture.

It is therefore an object of the present invention to provide a method for improving the resolving power of the lower layers of a multi-layer color film. A further gbject is to provide a novel multi-layer photographic These objects are accomplished by incorporating in an upper layer of a multi-layer film, a coloring material which absorbs a part but not all of the light which the lower layer or layers record.

The accompanying drawing shows in sectional views films constructed according to our invention.

The film used according to our invention consists of a suitable support such as cellulose ester, synthetic resin or paper, having on one side thereof suitable subbing layers and three superposed silver halide emulsion layers. In the usual sensitivity arrangement, the red-sensitive silver halide emulsion layer is coated on the subbing layer and that is followed by the green-sensitive emulsion layer and the blue-sensitive emulsion layer. A removable yellow coloring material is ordinarily contained in a layer between the blue-sensitive emulsion layer and the greensensitive emulsion layer, and other intermediate or overcoating layers may also be present. This sensitivity arrangement may be altered by coating the red-sensitive emulsion layer or the green-sensitive emulsion layer outermost, especially where the film is designed as a print material.

The silver halide emulsion layers may contain couplers incorporated in any suitable way, for example, in the manner described in Jelley and Vittum U. S. Patent 2,322,027. When such couplers are used, the cyanforming coupler will ordinarily be incorporated in the red-sensitive emulsion layer, the magenta-forming coupler in the green-sensitive emulsion layer and the yellowforming coupler in the blue-sensitive emulsion layer. It the film is to be used as a negative taking material colored couplers for masking purposes may be employed as described in Hanson U. S. Patent 2,449,966.

According to our invention, resolving power or definition or both are improved by incorporating in an upper emulsion layer of the film a material which may be a dye or pigment and which absorbs part of the light which a lower silver halide layer records but transmits light which the silver halide layers above the lower layer record. For example, in a multi-layer film having the sensitivity arrangement red, green, blue, from the support outerward, the blue-sensitive top layer may contain a magenta or reddish dye which absorbs part of the light which the green-sensitive layer records. Either the blue-sensitive layer or the green-sensitive layer may contain a cyan or bluish dye which absorbs part of the light which the redsensitive layer records. These dyes do not absorb light to which the layer in which they are incorporated is sensitive or the light to which any layer above the layer in which they are incorporated is sensitive.

The dye or pigment incorporated in the emulsion layer inevitably produces a loss in speed of the layer below that in which it is incorporated. For this reason, the density of the absorber incorporated in any layer should be held to the minimum required to give the necessary improvement in image sharpness. In a camera film, an optical density of 0.3 would be about the upper limit but in printing or duplicating films, an optical density of about 0.6 may be tolerated. An optical density of 0.6 means that the dye or pigment absorbs of the light impinging on it in the spectral region of maximum absorption of the absorbing material. Thus the absorbing material which we employ should not absorb more than about A of the light which impinges on it in the spectral region of maximum absorption of the dye or pigment.

Coloring materials which we may employ are the aluminum lake of aurin tricarboxylic acid and Prussian Blue. The aurin tricarboxylic acid is a magenta dye and is removed dnring processing by an alkali sulfite solution, for example, a developing solution. Prussian Blue is a bluish pigment which is removed in an alkaline developing solution containing iron sequestering agents such as ethylene diamine tetra-acetic acid.

The following examples illustrate the method of using the coloring materials according to our invention.

Example I Turnbulls Blue in gelatin was prepared by taking taneously a solution of 3.6 g. of ferrous ammonium sulfate in 36 cc. of water and a solution of 3.0 g. of potassium ferricyanide in 36 cc. of water. The solutions were run in slowly over a period of three minutes with continuous mechanical stirring. The dispersion was chilled until the gelatin was thoroughly set, then shredded and washed in running water for three hours to remove soluble by-products and excess potassium ferricyanide.

This disperson may be added to emulsion. The color is bleached by the alkali of the developer; materials forming complexes with ferric iron, such as ethylenediamine tetra-acetic acid or sodium fluoride, may be added to the developer, to avoid the possibility of stain from the ferric hydroxide which is formed.

Example 2 The dispersion of the aluminum lake of aurin tricarboxylic acid was prepared as follows.

Five-tenths g. of aurin tricarboxylic acid was dissolved in 1 cc. 20% sodium hydroxide and 15 cc. water. To this was added 0.75 g. aluminum sulfate (18H2O) which had first been dissolved in water, precipitated and redissolved by the addition of 20% sodium hydroxide solution.

The above combination was then added to cc. of 2.5% gelatin solution at 40 C. Vigorous stirring was maintained during the addition of the alkaline solution. The pH of the gelatin solution was kept between 5.0-5.5 by the addition of dilute sulfuric acid.

When all the alkaline solution had been added, 40 cc. of 10% gelatin was added. Stirring was continued for 5 minutes. The gelatin solution was chilled, shredded, and washed with cold water for 2 hours.

This may be added to the emulsion with very little desensitization. It is bleached in any developer con- 3. taining moderate amounts of sulfite or, if the film is processed only in color developer-low in sulfite; a separate sohltion of, for example, 10% sodium sulfite may be use The following example describes a complete film. strum ture made according to ourinventiorn;

Example 3 Starting with the support, the successive layers for a: negative material are as follows: x

1. Red-sensitive layer. A bromoiodide emulsion with silver halide corresponding to..86 g. sil ver per sq; meter. This emulsion is sensitized with. 3,3 dimethyl=9-ethyl= 4,5,4,5-dibenzthiacarbocyaninechloride, about .15 g.: per mole of silver halide, the exact amount dependingorr; the grain size of the emulsion; It contains aacyan'color former, 2%(4 amylphenoxybut'yrylarnino)4 '-'chlor'o-- 5-. methyl phenol, 650 mg. per sq. meter, dissolved in four times its Weight of dibutylphthalate;,thesolution of the coupler is dispersed in fine droplets in the emulsion.

2. Thesecond coat is anemulsion layer. with silver. halide corresponding to 1.07 g. silver per sq. meter: This is sensitized to green with. Z-diphenyIaminQ-SJ-I(.3; ethylbenzothiazolylidene -ethylidene] 4-' 5) thiaz'olo'ne, approximately .15 g. per mole of silver halide, the amountdepending on grain size of the emulsion. It contains as a red light absorber Prussian Blue in.acolloidal dispersion at a concentration of 0.10 g, per sq. meter. As a magentacolor former, there is added 1-(pEp-tert. butylphenoxylphenyl) 3 (inEp-toluenesulfonylaimi no]benzoylamino-S-pyrazolone, 550mg. per sq. meter, dissolved in four times its weight of dibutylphthalate.

3. The third coat is a dispersion .of-colloidal silver in gelatin, 100 mg. per sq. meter. v

4. The fourth coat is an unsensitized bromoiodide emulsion containing silver. halide corresponding; to. ,86 g. silver per sq. meter. To this there is addeda dis persion of the aluminum lake of auri'n tricarboxylie. acid in gelatin, .075 g. (calculated as freeacidtlper sq.- meter.- It contains a yellow color former, N(pbenzoylacetaminobenzenesulfonyl -N- Z-phenylpropyl -p-tert.- amylaniline, 1750 mg. per sq. meter, dissolved in four: times-its. weight of dibutylphthalate.

Our invention will now be described by ;reference to the accompanying drawing. Asshown in Fig. 1 thereof, 10 is a support having thereon a red-sensitive silver halide emulsion layer 11, a green-sensitives'ilver halide emulsion layer 12, a yellow filter layer 13v and. a bluesensitive silver halide emulsion layer 14.. The blue-- sensitive layer 14 contains a magnetadyewhich absorbs 4 part of the green light which the layer 12 records and therefore reduces scattering of green-- light.

Fig. 2 illustrates a similar structure in which the greensensitive layer 15 and the blue-sensitive layer 16 contain a cyan dye which absorbs part of the light which the red-sensitive layer llrecords and therefore reduces scattering of red light.

In; the modification shown in Fig. 3, the blue-sensitive layer 17 is adjacent thesupport,v the red-sensitive layer 18 is next and the green-sensitive layer 19 which contairisa cyan :dye or pigment is outermost. In this case the cyandye' or pigment in layer 19 reduces scattering of red light which records in layer 18 but does not affect the blue light which records in layer 17.

Fig.4 illustrates a modification in which the bluesensitive layer 17 is adjacent the. support, the greensensitive layer 20 is" iieXt and thered=sensitive layer 21 containing a magenta dye or pigment is outermost. In this case the. ma enter-dye or pigment absorbs part of thegreem lightbw'ich layer 20 records and thereby reduces scattering of green light.

The films described in. Figs. 3 and 4' are: intended for Pr i It .will, be understocd that the, modifications and eitamples included v herein are illustrative. only and that ourinvent'ion is to be taken as limited only-by the scope oftheappended claim.

A multi-layer photographic element capable of producing colored-images having improved definition, comprising a support having onone side thereof, silver halideemulsion layers separately sensitive, in order, to the red,: green, and blue spectral regions, said red-sensitive emulsion layer being adjacent said support and said green-sensitive emulsion layer containing Prussian Blue as a-Jred-light-absorbing material, said material absorbing not more than A of the red light impinging on it.

References Cited the file of this patent 

